Better abstraction for driver & file type handling

[charles-turner-1]

Okay, think this is more or less ready to go.

Stylistically I'm really not a fan of the if/else chain I've used to implement this, but I think it's going to be a bit of a pain to implement it 'more properly' - I'll open a separate PR doing so.

Originally posted by @charles-turner-1 in https://github.com/intake/intake-esm/issues/728#issuecomment-3070879270

TLDR; the CatalogFileDataReader in cat.py could do with a better abstraction, especially if we want to add support for more file types/drivers.